Detecting device for visual observation of a moving fabric

ABSTRACT

FOR USE IN FABRIC STRAIGHTENING APPARATUS INCORPORATING FABRIC STRAIGHTENING MEANS IS PROVIDED A DETECTOR DEVICE WHICH INCLUDES A GLASS GLATE WHICH IS SEMI-TRANSPARENT AND IS PLACED SUBSTANTIALLY PARALLEL AND CLOSE TO THE SURFACE OF A FABRIC TO BE INSPECTED, SUCH THAT A LIGHT SOURCE ARRANGED ON THE SIDE OF THE PLATE OPPOSITE THE FABRIC PROJECTS LIGHT RAYS THROUGH THE PLATE WHICH STRIKE THE FABRIC SURFACE, AS THE LATTER IS MOVED PAST THE PLATE, AT A PREDETERMINED ANGLE, SUCH THAT THE LIGHT RAYS ARE REFLECTED BY THE FABRIC ONTO THE GLASS AND THE INTENSITY OF THE RELECTED LIGHT RAYS CAN BE DETECTED BY FIRST AND SECOND DETECTOR HEADS ARRANGED ON THE SAME SIDE OF THE PLATE AS THE LIGHT SOURCE AND SYMMETRICALLY WITH RESPECT THERETO, THE DETECTOR HEADS BEING CONNECTED IN A BRIDGE CIRCUIT OPERABLE TO DETECT VARIATIONS IN THE INTENSITIES OF THE RELECTED LIGHT RAYS CAUSED BY IRREGULARITES IN THE LIGHT REFLECTING FABRIC TO CONTROL THE FABRIC STRAIGHTENING MEANS.

12, 1971 I v IIH .EICKEN DETECTING DEVICE FOR-VISUAL OBSERVATION OF A MOVING-FABRIC "ori inal med June 4, 1965 v 3 Sheets-Sheet 1 Iigl.

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7 DETECTING DEVICE FOR VISUAL OBSERVATION or A MOVING FABRIC Originai Filed Jung 4, .1965 i s Sheets-Sheet 2 Jan.12, 1 97 EICKEN 3,554,656

DETECTING DEVICE. FOR VISUAL- OBSERVATION OF A MOVING FABRIC Original Filed June ,4. 1965 3 Sheets-Sheet s United States Patent 3,554,656 DETECTING DEVICE FOR VISUAL OBSERVATION OF A MOVING FABRIC Henri Eicken, Chemin de Malombre, Geneva, Switzerland Continuation of application Ser. No. 461,433, June 4, 1965. This application Apr. 10, 1969, Ser. No. 837,976 Claims priority, application Switzerland, June 8, 1964, 7,468/64 Int. Cl. G01n 21/32 US. Cl. 356-238 2 Claims ABSTRACT OF THE DISCLOSURE For use in fabric straightening apparatus incorporating fabric straightening means is provided a detector device which includes a glass glate which is semi-transparent and is placed substantially parallel and close to the surface of a fabric to be inspected, such that a light source arranged on the side of the plate opposite the fabric projects light rays through the plate which strike the fabric surface, as the latter is moved past the plate, at a predetermined angle, such that the light rays are reflected by the fabric onto the glass and the intensity of the reflected light rays can be detected by first and second detector heads arranged on the same side of the plate as the light source and symmetrically with respect thereto, the detector heads being connected in a bridge circuit operable to detect variations in the intensities of the reflected light rays caused by irregularities in the light reflecting fabric to control the fabric straightening means.

This application is a continuation of Ser. No. 461,433 filed June 4, 1965, now abandoned.

The present invention relates to a detecting device in an equipment for the visual observation of a moving web of fabric or threads and the automatic control of a straightening mechanism.

A web of fabric or threads very often undergoes deformation during the various manufacturing operations and it is necessary to straighten it during the finishing operations.

H but this was formerly possible to carry out this operation by hand, for example during drying, it is no longer the case at present with dryers and wefts working at speeds reaching several hundreds of metres per minute. At speeds exceeding 25 or 30 metres per minute, the operator can no longer directly observe the fabric and effect by hand the straightening mechanism.

There have been proposed various devices which make use for example of stroboscopic effects permitting the visual observation of webs, and others which make use of photoelectric cells controlled by luminous sources the light of which passes through the fabrics and controlling in their turn a straightening mechanism. These devices may be used with a certain amount of success for fabrics of light texture, but they do not operate with heavy fabrics or with all colors.

The invention has for object to overcome these deficiencies and to provide a device which may be employed with fabrics of any texture or color.

The device of the present invention is characterized in that it comprises a semi-transparent glass plate, a luminous source which illuminates the surface of the fabric at a predetermined angle of incidence through the glass plate so that the light reflected by the surface of the fabric produces in the glass plate an image of said surface, two or 3,554,656 Patented Jan. 12, 1971 'ice more detecting devices or scanning heads mounted symmetrically one with respect to the other and relative to the luminous source, receiving said image and each comprising a measuring cell mounted centrally in the head and the opening of which is directed towards the image in the glass plate to detect the variations of light emitted by this image, the two cells being connected by a bridge circuit the variable direct output voltage of which is applied to an amplifier, then to an integrator and to a modulator to be transformed into a variable alternating voltage of reversed phase controlling the visual observation unit and the straightening mechanism.

The accompanying drawing shows, by way of example, two embodiments of the device of the invention.

FIG. 1 is a simplified block diagram of equipment according to the invention.

FIG. 2 is a plan view of a first embodiment of scanning head, certain members being omitted.

FIG. 3 is a section along line 33 of FIG. 2.

FIG. 4 is a plan view of a second embodiment, certain members being omitted.

FIG. 5 is a section along line '55 of FIG. 4.

The equipment shown schematically in FIG. 1 includes two detecting devices I and III and mounted in front of a moving fabric to be controlled, two amplifiers H and IV, an integrator V of the signals coming from the amplifiers -I I and IV, and a modulator VI transforming the signals coming from the integrator V into control signals for a unit VI 'I automatically controlling a straightening mechanism and for a unit VIII for the visual observation of the fabric. All the elements H to VIII may be constructed in the usual known manner.

The detecting device shown in FTGS. 2 and 3 (device I or III of the equipment according to FIG. 1) includes a supporting plate 1 having at its center a circular opening 2. A circular plate 3 is mounted on the supporting plate 1 and also has its center a circular opening which is closed by a semi-transparent glass plate 4. The plate 3 is held on plate 1 by screws 5 and washers 6 so as to be able to rotate about its center under the action of a lever 7. Once in the desired position, the plate 3 may be blocked by the screws 5. Plate 3 carries three sliding supports 8 which respectively carry a luminous source 9 and two detecting heads 10 and 11. The luminous source 9 is constituted by an electric bulb and a reflector surrounded by a screen which guides the light rays. The detecting heads 10 and 11 each include a photoresistant measuring cell 12 which may receive through its central opening the light of the source 9 reflected in the plate 4. Slides 13 in each support 8 permit the fixing of luminous source and the detecting heads 10 and 11 at different angles. A lid 14, not shown in FIG. 2, carries a multiple plug 15 for connecting the outer leads to the various members and protects the whole unit against any light arriving from outside. The device is fixed to rings 16 which may slide on supporting bars 17 so as to be placed in front of the fabric to be controlled. Rotation of the plate 3 permits adjusting the incident angle of the luminous source according to the texture of the fabric. The device described operates in the following manner:

Two devices identical with the one described are mounted in front of the fabric. The surface of the fabric is illuminated under a skimming incidence by the light rays produced by the source 9 which strikes said surface at a predetermined angle. This light is reflected by the surface of the fabric and reproduces the image of this surface in the plate 4. The photoresistant cells of the two heads 10 and 11 are electrically connected to a bridge circuit. The angle of inclination of the heads 10 and 11 is chosen in relation to the inclination of the luminous source 9 in order to obtain maximum reflection.

When the image reflected in the plate 4 is identical for the two detecting cells, the bridge is balanced and no output voltage appears at its terminals. Such is the case, for example, when the weft of the fabric is strictly straight, giving for both cells an identical image of the fabric illuminated by the source and thus an equal intensity of reflected light. On the other hand, if the fabric is deformed in any way, the intensity of the image reflected in the plate 4 differs from one cell to the other and a negative or positive voltage appears at the output terminals of the bridge. This voltage is sent by the detecting device I into the amplifier II and by the detecting device III into the amplifier IV, these amplifiers being of direct current and the voltage being applied between a grid and the mass. The distances between the luminous source 9, the detecting heads 10 and 11 and the plate 4 being fixed, the reflected image is always disposed at the same distance relative to the detecting heads even if the distance between the fabric and the mirror varies. Thus, one obtains an image whatever the conditions may be. Moreover, since the reflected light detected by the heads is not directly the light reflected by the fabric but that of the image reflected in the plate, the variations of intensity due to different colors of the fabric no longer play any role. The device is thus very accurate as a result of the clearness of the image and the variations of the light emitted by this image, and this for a fabric of any color.

The amplifiers II and IV may be of standard construction. Their output voltage is applied to the integrator V and to the modulator VI which are also of standard construction, and serve to transform the variations of the direct voltage of the amplifiers into variations of alternating voltage. This latter has an amplitude proportional to the difference between the output voltage of the amplifier and a reference voltage and its phase is reversed according to the amplitude of this difference. This alternating voltage serves to start up thyratrons of units VII and VIII.

The unit VII controls a fabric straightening mechanism. It may include, in standard manner, thyratrons or cold cathode tubes with starting and blocking devices for the thyratrons. It is controlled by the alternating voltage of reversed phase arriving from the modulator VI. This unit may also be arranged so as to break by a relay contact the supply of the cold cathode tubes when the fabric is immobilized.

The visual observation unit VIII may include thy- ;atrons or cold cathode tubes mounted in normal manner and fed by the alternating voltage of reversed phase arriving from modulator VI. It may include for example sets of signalling lamps which, through their lighting, indicate very clearly the exact position of the fabric to be controlled or the position of certain elements of the fabric, for example prints.

In this embodiment, the reflected light detected by the detecting heads is not directly the light reflected by the fabric but that of the image reflected in the plate 4, and thus variations of intensity due to different colors of the fabrics no longer play any role and the device is thus very accurate for fabrics of any color. This accuracy may further be considerably increased by adding a third detecting head which has the objective to compensate the slightest variations of the light reflected in the plate 4.

Such an embodiment is shown in FIGS. 4 and 5 and includes a supporting plate 18 having at its center a circular opening 19. A circular plate 20 is mounted on the supporting plate 18 and also has at its center a circular opening which is closed by a glass plate 21. The plate 20 is held on the plate 18 by screws 22. The plate 20 carries sliding supports carrying respectively a luminous source 23 (not shown in FIG. 4) and two first detecting heads 24 and 25. The source 23 is constituted by an electric bulb and a reflector surrounded by a screen which guides the light rays. The detecting heads 24 and 25 each include a photoresistant measuring cell which may receive through its central opening the light of the source 23 reflected by the plate 21. Slides, not shown, permit fixing of the detecting heads 24 and 25 at different angles. A lid 26, not shown in FIG. 4, carries a multiple plug 27 for connecting the outer leads to the various members and protects the whole unit against any light arriving from outside. The source 23 is disposed outside the lid 26 to facilitate its cooling. The lid may carry a filter allowing the passage of the light from the source within a definite range of wave lengths. The members described are fixed to rings 28 which may slide on supporting bars 29 so as to be placed in front of the fabric to be controlled.

This second embodiment as so far described is similar to the first embodiment. However, it further includes a third detecting head 30 mounted in the plane of the luminous source and between the two first detecting heads 24 and 25, so as to receive the light reflected by the plate 4. As with the preceding ones, this head includes a photoresistant measuring cell.

Two devices identical to the one described are mounted in front of the fabric. The surface of the fabric is illuminated under a skimming incidence by the luminous rays produced by the source 23 which strikes the said surface at a predetermined angle. This light is reflected by the surface of the fabric and reproduces the image of this surface in the plate 21. The photoresistant cells of the heads 24, 25 and 30 are electrically connected to a bridge circuit. The angle of inclination of the heads 24, 25 and 30 is chosen in relation to the inclination of the luminous source 23 to obtain maximum reflection.

As in the first embodiment, when the image reflected in the plate 21 is identical for the two detecting cells 24 and 25, that is to say when the weft is strictly straight, the bridge is balanced and no output voltage appears at its terminals. On the other hand, if the fabric is deformed in any way, the intensity of the light reflected in the plate differs from one cell to the other and a negative or positive voltage appears at the output terminals of the bridge. The third head 30 has for object to compensate the slightest variations of the light reflected in the plate 21 due to the various textures or colors of the fabric, which increases the accuracy of the device.

The use of the third detecting head has also proved very beneficial when, as a result of any accident, the reflecting plate 21 is damaged or removed, or again when this plate is dirty. In these cases, the device retains all its accuracy and may be used even without the plate 21.

What is claimed is:

1. A detecting device in equipment for the observation of a moving web of textile or other fabric and the automatic control of a weft straightening mechanism, said device comprising a glass plate which is semitransparent, lluminating means mounted on one side of the plate for 1lluminating a surface of the web at a predetermined angle of incidence through the plate so that light rays are reflected by the surface of the Web, two detecting heads mounted on the same side of the plate as the illuminating means and symmetrically arranged relative thereto for receiving the light rays reflected by the web, each said head comprising a measuring cell mounted centrally therein and having an opening directed towards the reflected light rays to detect the variations of light reflected by said web, a bridge circuit electrically coupled with each of said detecting heads, an amplifier electrically coupled with said bridge circuit for receiving a direct voltage, and integrator and a modulator electrically coupled with said amplifier for transforming said variable direct voltage into a variable alternating voltage of reversed phase for controlling an observation unit and the straightening mechanism.

2. A device according to claim 1 further comprising a third detecting head mounted in the plane of the illumi- 6 nating means, so as to receive the light reflected by the 3,139,911 7/1964 Breitmeier 8814(Y)X plate, and connected to the bridge circuit to compensate 3,193,688 71965 Morton et a1 8814(Y)X for the variations of intensity of the light reflected by the RONALD L. WIBERT, Primary Examiner plate.

References CW1 5 0. B. CHEW 11, Assistant Examiner UNITED STATES PATENTS 3,077,656 2/1963 Mahlo 88--14(Y)AX 250419 CL 3,135,867 6/1964 Daneff 250219(Web) 

